On 2/5/23 12:36 PM, PDXer wrote:

I received the RF Demo kit for NanoVNA. The cables are indeed fiddly to attach on the pcb board, but I am getting used to it. Just hope that it will last for some long time rather than get mangled, and ruin my investment for the learning.
Anyhow I got it to calibrate OK for Open, Short and Load with the Demo Kit board and supplied cables.
But when I tried to read for the 30Mhz Band Pass Filter, the readings on the screen didn't come out what is indicated on the board. It was more squiggly curve type graphs on the display. I tried to change the settings with the SPAN and SCALE in the menu, but it made it actually worse or was just showing straight horizontal line.
Could someone please explain, what settings the VNA must have to display nice sharp dip of the graph as on the board?

That would likely be the S11 magnitude - in the passband, the filter lets the RF through, so it sees the 50 ohms on the other side, so reflected power is small (i.e. good match). Outside the passband, the filter probably reflects the power back, so S11 is close to 1.

S21 should show the bandpass characteristic (i.e. small magnitude (large negative dB) outside the passband and big magnitude (small negative dB)) inside the passband.